1. Technical Field
The present invention relates to a technique of driving a pixel so as to be turned ON or OFF in each of a plurality of subfields.
2. Related Art
To express halftones in an electrooptical device having display elements such as liquid crystal elements as pixels, a technique using subfield driving has been proposed. The technique using subfield driving is a technique of expressing halftones by driving a pixel so as to be turned ON or OFF in each of a plurality of subfields obtained by dividing a frame (field) and varying the ratio of the ON driving time to the OFF driving time in one frame (for example, JP-A-2007-148417 (Patent Document 1)).
As in the technique described in Patent Document 1, in subfield driving, a subfield code (hereinafter referred to as an SF code) that defines the details of driving (ON or OFF) of the pixels in the subfields of one frame is used. Based on this SF code, an ON voltage or an OFF voltage is applied to the liquid crystal element of each pixel. When the gray levels designated for adjacent pixels are different from each other, in periods of subfields with different details of driving in each SF code, a transverse electric field is generated between the adjacent pixels due to a difference between the ON voltage and the OFF voltage. Owing to the influence of the transverse electric field, disclination is generated between the adjacent pixels and affects display. As a result, the more the subfields with different details of driving in adjacent pixels, the greater the influence of disclination on display, the disclination generated between the adjacent pixels.
Here, to express a large number of gray levels with a small number of subfields, it is necessary to assign weights to the times of the subfields by making the times of the subfields greatly differ from each other. In such a case, the details of driving of long time subfields may differ from each other between the gray levels which are next to each other. The gray levels of adjacent pixels sometimes become the gray levels which are next to each other. However, in the above-described case, the time in which the transverse electric field is generated is also lengthened, and the influence of disclination on display, the disclination generated between the adjacent pixels, becomes greater.